The present invention relates to novel anticancer agents, their stereoisomers, their polymorphs, their pharmaceutically acceptable salts, and their pharmaceutically acceptable solvates. The present invention more particularly relates to novel derivatives of Andrographolide, their stereoisomers, their polymorphs, their pharmaceutically acceptable salts, and their pharmaceutically acceptable solvates. The novel derivatives of Andrographolide have the general formula (I), 
where R1, R2 and R3 may be same or different and independently represent hydrogen or substituted or unsubstituted groups selected from alkyl, aryl, heteroaryl, aralkyl, heteroaralkyl, alkanoyl, alkenoyl, aroyl, heteroaroyl, sulfonyl group or a group xe2x80x94(CO)xe2x80x94Wxe2x80x94R4 where W represents O, S, or NR5, wherein R5 represents hydrogen or (C1-C6)alkyl group, R4 represents substituted or unsubstituted groups selected from alkyl, aryl, aroyl, or aralkyl or R2 and R3 together form a substituted or unsubstituted 3 to 7 membered cyclic structure containing carbon and oxygen atoms.
The andrographolide derivatives represented by general formula (I) defined above of the present invention are useful for treating cancer and other proliferative diseases including but not limited to herpes simplex virus types I and II, (HSVI and HSVII) and human immunodeficiency virus (HIV). The compounds of the present invention are also useful in the treatment of psoriasis, restonosis, atherosclerosis and other cardiovascular disorders. The compounds of the present invention are also useful as antiviral, antimalarial, antibacterial, hepatoprotective, immunomodulating agents and for treatment of metabolic disorders. The anticancer activity exhibited may be through cytotoxic activity, antiproliferation, cell cycle kinase inhibition or may be through cell differentiation.
The compounds of formula (I) are also useful for the treatment and/or prophylaxis of insulin resistance (type II diabetes), leptin resistance, impaired glucose tolerance, dyslipidemia, body weight reduction, disorders related to syndrome X such as hypertension, obesity, insulin resistance, coronary heart disease and other cardiovascular disorders.
The present invention also relates to pharmaceutical compositions containing compounds of general formula (I) or mixtures thereof.
The present invention also relates to a process for the preparation of the above defined compounds of general formula (I), their stereoisomers, their polymorphs, their pharmaceutically acceptable salts, and their pharmaceutically acceptable solvates.
The plant Andrographis paniculata is extensively used in traditional medicine as a bitter tonic, febrifuge and in bowel complaints (Glossary of Indian Medicinal Plants., Ed. R. N. Chopra, S. L. Nayar, I. C. Chopra, p18, 1996; The useful plants of India, Ed. By S. B. Ambasta, p39, 1992). The plant is useful in the treatment of bacterial infections (Int. J. Crude Drug Res. 1990, 28(4), p273-283; Drugs of the Future. 1990, 15(8) p809-816). It is reported to possess antimalarial (Int. J. Pharmacognosy, 1992, 30(4), p263-274; J. Ethnopharmocol., 1999, 64(3), p249-254) and immunostimulant activity (J. Nat. Prod., 1993, 56(7), p995-999). The plant has also been shown to be antithrombotic (Chinese Medical Journal 1991, 104(9), p770-775) and inhibit stenosis and restenosis after angioplasty in the rat (Chinese Medical Journal, 1994, 107(6), p464-470). It is also known that the plant extract and its constituents exhibit promising hepatoprotective activity (Planta Medica, 1987, 53(2), p135-140). Significant attention has been paid by several research groups on A. paniculata in recent years due to its cytotoxic, antitumorogenic, cell differentiation inducing activities and anti-HIV activities.
Andrographolide having the formula (II), 
the major constituent of the plant A. paniculata was first isolated by Gorter (Rec. trav. chim., 1911, 30, p151-160). 
The extracts of the dried plant, which contain compounds of formula (III), have been assayed for the ability to decrease expression and phosphorylation of p34cdc2 kinase, cyclin B and c-Mos for treating or preventing pathogenecity of diseases such as AIDS, Alzheimer""s disease and hepatitis (WO 96/17605).
Cell cycle kinases are naturally occurring enzymes involved in regulation of the cell cycle (Progress in Cell Cycle Research, 1995, 1, p351-363). Typical enzymes include the cyclin-dependent kinases (cdk) cdk1, cdk2, cdk4, cdk5, cdk6 and wee-1 kinase. Increased activity or temporarily abnormal activation of these kinases has been shown to result in development of tumors and other proliferative disorders such as restenosis. Compounds that inhibit cdks, either by blocking the interaction between a cyclin and its kinase partner or by binding to and inactivating the kinase, cause inhibition of cell proliferation and are thus useful for treating tumors or other abnormally proliferating cells.
The extract of A. paniculata was found to show significant cytotoxic activity against KB and P388 cells. Interestingly, Andrographolide of the formula II, has been shown for the first time to have potent cytotoxic activity against KB as well as P388 lymphocytic leukemia, where as 14-deoxy-11,12-didehydroandrographolide and neoandrographolide having the formulae IV and V 
where R represents xcex2-D-glucose moiety, have shown no cytotoxic activity in tumor cell lines (J. Sci. Soc. Thailand, 1992, 18, p187-194).
The methanolic extract of the aerial parts of A. paniculata Nees showed potent cell differentiation inducing activity on mouse myeloid leukemia (M1) cells (Chem. Pharm. Bull. 1994, 42(6) 1216-1225).
Japanese patent application JP 63-88124, discloses a mixture of at least two compounds of formula VIa and VIb, 
where R1, R2, R3, R4 and R5 represent hydrogen or lower alkanoyl group and their activity as antitumorogenic agents.
DASM (Dehydroandrographolide Succinic acid monoester) prepared from Andrographolide of the formula II is found to be inhibiting HIV virus and nontoxic to the H9 cell at the concentrations of 50-200 xcexcg/ml and was inhibitory to HIV-1(IIIB) at the minimal concentration of 1.6-3.1 xcexcg/ml (Proc. Soc. Exp. Biol. Med., 1991, 197, p59-66).
The plant Andrographis paniculata is also reported to inhibit proprotein convertases-1, -7 and furin possibly by suppressing the proteolytic cleavage of envelope glycoprotein gp 160 of HIV, which is known to be PC-mediated, particularly by furin and PC (Biochem. J., 1999, 338, 107-113)
In International patent application WO 91/01742, compositions containing one or more ingredients obtained from the plants Valeariana officinalis and/or A. paniculata were disclosed to have antiviral, antineoplastic, antibacterial and immunomodulatory activity.
Although several novel Andrographolide derivatives have been prepared, screened and reported in the above said prior-art literature for their anticancer activity, they are not showing interesting activity.
With an objective of preparing novel andrographolide derivatives useful for treating cancer, HSV, HIV, psoriasis, restonosis, atherosclerosis, cardiovascular disorders and as antiviral, antimalarial, antibacterial, hepatoprotective, immunomodulating agents and for treatment of metabolic disorders, which are potent at lower doses and having better efficacy with lower toxicity, we focussed our research efforts in preparing the novel Andrographolide derivatives of the formula (I) as defined above.
The main objective of the present invention is, therefore, to provide novel Andrographolide derivatives of the formula (I) as defined above, their stereoisomers, their polymorphs, their pharmaceutically acceptable salts, their pharmaceutically acceptable solvates and pharmaceutical compositions containing them or their mixtures.
Another objective of the present invention is to provide pharmaceutical compositions containing compounds of the formula (I), their stereoisomers, their polymorphs, their pharmaceutically acceptable salts, their pharmaceutically acceptable solvates, containing them or their mixtures in combination with suitable carriers, solvents, diluents and other media normally employed in preparing such compositions.
Still another objective of the present invention is to provide pharmaceutical compositions containing compounds of the formula (I), their stereoisomers, their polymorphs, their pharmaceutically acceptable salts, their pharmaceutically acceptable solvates, containing them or their mixtures in combination with one or more pharmaceutically acceptable active compounds with suitable carriers, solvents, diluents and other media normally employed in preparing such compositions.
Still another objective of the present invention is to provide a process for the preparation of Andrographolide derivatives of the formula (I) as defined above, their stereoisomers, their polymorphs, their pharmaceutically acceptable salts, their pharmaceutically acceptable solvates and pharmaceutical compositions containing them or their mixtures having enhanced activity with little or no toxic effect or reduced toxic effect.
Accordingly, the novel derivatives of Andrographolide of the present invention have the general formula (I) 
where R1, R2 and R3 may be same or different and independently represent hydrogen or substituted or unsubstituted groups selected from alkyl, aryl, heteroaryl, aralkyl, heteroaralkyl, alkanoyl, alkenoyl, aroyl, heteroaroyl, sulfonyl group or a group xe2x80x94(CO)xe2x80x94Wxe2x80x94R4 where W represents O, S, or NR5, wherein R5 represents hydrogen or (C1-C6)alkyl group, R4 represents substituted or unsubstituted groups selected from alkyl, aryl, aroyl, or aralkyl or R2 and R3 together form a substituted or unsubstituted 3 to 7 membered cyclic structure containing carbon and oxygen atoms; their stereoisomers, their polymorphs, their pharmaceutically acceptable salts and their pharmaceutically acceptable solvates.
Suitable groups represented by R1, R2 and R3 include substituted or unsubstituted, linear or branched (C1-C8)alkyl group such as methyl, ethyl, n-propyl, iso-propyl and the like; aryl group such as phenyl, substituted phenyl and the like, the aryl group may be substituted; heteroaryl group such as pyridyl, furyl, thiophenyl and the like, the heteroaryl group may be substituted; aralkyl such as benzyl, phenethyl and the like, the aralkyl group may be substituted; heteroaralkyl group such as pyridylmethyl, pyridylethyl, furanmethyl, furanethyl and the like, the heteroaralkyl group may be substituted; (C2-C8) alkanoyl group such as ethanoyl, propanoyl, butanoyl and the like, the (C2-C8) alkanoyl group may be substituted; (C3-C8) alkenoyl group such as propenoyl, butenoyl, pentenoyl and the like, (C3-C8)alkenoyl group may be substituted; aroyl group such as benzoyl and the like, the aroyl group may be substituted; heteroaroyl group such as pyridyl carbonyl, furyl carbonyl and the like; the heteroaroyl group may be substituted; and sulfonyl group such as methanesulfonyl, benzenesulfonyl, p-toluenesulfonyl and the like, the sulfonyl group may be substituted.
The substituents on R1, R2 and R3 may be selected from cyano, hydroxy, nitro, halogen atom such as fluorine, chlorine or bromine; substituted or unsubstituted group selected from (C1-C8)alkyl such as methyl, ethyl, propyl, butyl and the like, the substituents of (C1-C8)alkyl may be selected from halogen atom, hydroxy, nitro, cyano, amino, phenyl or (C1-C6)alkoxy groups; amino, mono or disubstituted amino group, the substituents of the amino group may be selected from hydroxy or (C1-C6) alkoxy groups; alkanoyl group such as ethanoyl, propanoyl, butanoyl and the like; (C1-C6) alkoxy group such as methoxy, ethoxy, propyloxy, butyloxy and the like; aroyl group such as benzoyl and the like; acyloxy group such as acetyloxy, propanoyloxy, butanoyloxy and the like; aryl group such as phenyl, naphthyl and the like, the aryl group may be mono or disubstituted and the substituents may be selected from (C1-C6)alkyl, halogen atom, amino, cyano, hydroxy, nitro, trifluoroethyl, thio, thioalkyl, alkylthio and (C1-C6)alkoxy groups; heteroaryl group such as pyridyl, furyl, thienyl and the like; mono(C1-C6)alkylamino group such as CH3NH, C2H5NH, C3H7NH, and C6H13NH and the like; di(C1-C6)alkylamino group such as (CH3)2N, (C2H5)NCH3 and the like; acylamino groups such as CH3CONH, C2H5CONH, C3H7CONH, C4H9CONH, and C6H5CONH; arylamino group such as C6H5NH, (C6H5)NCH3, C6H4(CH3)NH, C6H4(Hal)NH and the like; aralkylamino group such as C6H5CH2NH, C6H5CH2CH2NH, C6H5CH2NCH3 and the like; alkoxycarbonylamino group such as C2H5OCONH, CH3OCONH and the like; aryloxycarbonylamino group such as C6H5OCONH, C6H5OCONCH3, C6H5OCONC2H5, C6H4(CH3)OCONH, C6H4(OCH3)OCONH, and the like; aralkoxycarbonylamino group such as C6H5CH2OCONH, C6H5CH2CH2OCONH, C6H5CH2OCON(CH3), C6H5CH2OCON(C2H5), C6H4(CH3)CH2OCONH, C6H4(OCH3)CH2OCONH and the like; or COOR, where R represents hydrogen or (C1-C6)alkyl groups.
When the aryl group is disubstituted, the two substituents on the adjacent carbon atoms may form a linking group such as xe2x80x94Xxe2x80x94CH2xe2x80x94Yxe2x80x94, or xe2x80x94Xxe2x80x94CH2xe2x80x94CH2xe2x80x94Yxe2x80x94, where X and Y may be same or different and independently represent O, NH, S or CH2.
When the groups represented by R1, R2 or R3 are multisubstituted, the substituents present on the two adjacent carbons may form a linking group xe2x80x94Xxe2x80x94(CR6R7)nxe2x80x94Yxe2x80x94 where R6 and R7 represent (C1-C8)alkyl such as methyl, ethyl and the like, X and Y may be same or different and independently represent C, O, S, or NH; and n=1 or 2.
Suitable groups represented by R4 include substituted or unsubstituted (C1-C6)alkyl such as methyl, ethyl, n-propyl and the like; aryl group such as phenyl, substituted phenyl and the like, the aryl group may be substituted; aralkyl such as benzyl, phenethyl and the like, the aralkyl group may be substituted; and aroyl group such as benzoyl and the like, the aroyl group may be substituted. The substituents on the alkyl group, aromatic moiety of the aryl group, aralkyl group or aroyl group include halogen atom such as fluorine, chlorine, and bromine; amino group, cyano, hydroxy, nitro, trifluoroethyl, (C1-C6)alkyl, and (C1-C6)alkoxy.
Pharmaceutically acceptable salts forming part of this invention include salts of the carboxylic acid moiety such as alkali metal salts like Li, Na, and K salts, alkaline earth metal salts like Ca and Mg salts, salts of organic bases such as lysine, arginine, guanidine, diethanolamine, choline and the like, ammonium or substituted ammonium salts, and aluminum salts. Salts may include acid addition salts where appropriate which include, sulphates, nitrates, phosphates, perchlorates, borates, hydrohalides, acetates, tartrates, maleates, citrates, succinates, palmoates, methanesulphonates, benzoates, salicylates, hydroxynaphthoates, benzenesulfonates, ascorbates, glycerophosphates, ketoglutarates and the like. Pharmaceutically acceptable solvates may be hydrates or comprising other solvents of crystallization such as alcohols.
Particularly useful compounds according to present invention include;
8,17-epoxy andrographolide;
3,14,19-triacetyl 8,17-epoxy andrographolide;
3,14,19-tripropionyl 8,17-epoxyandrographolide;
3,14,19-tris chloro acetyl 8,17-epoxy andrographolide;
8,17-epoxy andrographolide 3,19-acetonide;
14-methoxy 3,19-diacetyl 8,17-epoxy andrographolide;
14-cinnamoyl 3,19-dihydroxy 8,17-epoxy andrographolide;
14-cinnamoyl 3,19-dipropionyl 8,17-epoxy andrographolide;
14-[4xe2x80x2-methoxycinnamoyl]3,19-dipropionyl 8,17-epoxy andrographolide;
8,17-epoxy 14-[3xe2x80x2,4xe2x80x2-dimethoxycinnamoyl]3,19-dipropionyl andrographolide;
14-[3xe2x80x2,4xe2x80x2-methylene dioxy cinnamoyl]3,19-dipropionyl 8,17-epoxy andrographolide;
14-[N-Boc glycinyl]8,17-epoxy andrographolide;
14-[N-Boc glycinyl]3,19-dipropionyl 8,17-epoxy andrographolide;
19-trityl 8,17-epoxy andrographolide;
3-acetyl 8,17-epoxy Andrographolide;
3,14-diacetyl 8,17-epoxy Andrographolide;
14,19-diacetyl 8,17-epoxy Andrographolide;
3,14-dipropionyl 8,17-epoxy Andrographolide;
14-[4S,5R(N-1-butoxycarbonyl)-2,2-dimethyl-4-phenyl-5-oxazolidine]carbonyl-3,19-diacetyl-8,17-epoxy andrographolide; and
14-[2xe2x80x2-acetoxy-3xe2x80x2-N-acetylamino-3xe2x80x2-phenyl]propanoyl-3,19-diacetyl-3,17-epoxyandrographolide.
Cinnamoyl is propenoyl substituted by phenyl.
The present invention also provides a process for the preparation of novel derivatives of Andrographolide of the general formula (I) where R1, R2 and R3 may be same or different and independently represent hydrogen or substituted or unsubstituted groups selected from alkyl, aryl, heteroaryl, aralkyl, heteroaralkyl, alkanoyl, alkenoyl, aroyl, heteroaroyl, sulfonyl group or a group xe2x80x94(CO)xe2x80x94Wxe2x80x94R4 where W represents O, S, or NR5, wherein R5 represents hydrogen or (C1-C6)alkyl group, R4 represents substituted or unsubstituted groups selected from alkyl, aryl, aroyl, or aralkyl or R2 and R3 together form a substituted or unsubstituted 3 to 7 membered cyclic structure containing carbon and oxygen atoms, their stereoisomers, their polymorphs, their pharmaceutically acceptable salts and their pharmaceutically acceptable solvates, which comprises:
(i) epoxidising Andrographolide of the formula (II) 
by conventional methods to form a compound of formula (VII), 
(ii) reacting the compound of formula (VII) with R1xe2x80x94L, R2xe2x80x94L and R3xe2x80x94L, where R1, R2 and R3 may be same or different and independently represent hydrogen or substituted or unsubstituted groups selected from alkyl, aryl, heteroaryl, aralkyl, heteroaralkyl, alkanoyl, alkenoyl, aroyl, heteroaroyl, sulfonyl group or a group xe2x80x94(CO)xe2x80x94Wxe2x80x94R4 where W represents O, S, or NR5, wherein R5 represents hydrogen or (C1-C6)alkyl group, R4 represents substituted or unsubstituted groups selected from alkyl, aryl, aroyl, or aralkyl and L represents a leaving group such as hydroxy, halogen atom like fluorine, chlorine, bromine, or iodine; p-toluenesulfonate, methanesulfonate, trifluoromethanesulfonate, acyl group such as acetate, propanoate, butanoate and the like, to produce a compound of formula (I), and if desired,
(iii) protecting the hydroxy groups present on carbons 3 or 19 or 3 and 19 together in the compound of formula (VII) with suitable protecting groups using conventional methods to produce a compound of formula (VIII), 
where P1 and P2 may be same or different and represent hydrogen, trityl, t-butyl dimethyl silyl, pivaloyl and the like, or esters such as acetate, propionate, benzoate and the like or together may form methylene dioxy, acetonide, benzilidine and the like, (iv) reacting the compound of formula (VIII) defined above with compound of formula (IX)
R1xe2x80x94Lxe2x80x83xe2x80x83(IX)
where R1 and L have the meanings given above to produce a compound of formula (X), 
where R1, P1 and P2 are as defined earlier,
(v) deprotecting the compound of formula (X) by conventional methods to produce a compound of formula (XI), 
where R1 has the meaning given above,
(vi) reacting the compound of formula (XI) where R1 has the meaning given above with R2xe2x80x94L and/or R3xe2x80x94L, where R2, R3 and L are as defined above to produce a compound of formula (I), and if desired,
(vii) converting compound of formula (I) into their stereoisomers, pharmaceutical salts or pharmaceutical solvates by conventional methods.
The epoxidation of a compound of formula (II) may be carried out in the presence of oxidising agents such as per acids which may selected from m-chloroperbenzoicacid, p-nitro perbenzoic acid, mono per phthalic acid, peroxy lauric acid, peroxy acetic acid, magnesium mono per phthalate; peroxides such as hydrogen peroxide of various strengths, t-butyl hydroperoxide and the like; iodine and bromine in presence of silver salts and other epoxidising agents such as N-chlorosuccinimide, N-bromosuccinimide, N-bromoacetamide, or dimethyl dioxirane may be used. During the epoxidation conventional solvents such as methanol, ethanol, chloroform, dichloromethane, tetrahydrofuran, dimethyl formamide (DMF), dioxane and the like or their mixtures may be used. The reaction may be carried out at a temperature in the range of xe2x88x9220xc2x0 C. to 80xc2x0 C., preferably in the range of xe2x88x9220xc2x0 C. to 60xc2x0 C.
The reaction of a compound of formula (VII) with R1xe2x80x94L, R2xe2x80x94L and R3xe2x80x94L to produce a compound of formula (I) may be carried out in the presence of dicyclohexylcarbo-diimide (DCC), diethyl azadicarboxylate (DEAD), diisopropyl azadicarboxylate (DLAD), ethyl chloro formate or the like. The reaction may be carried out in the absence or presence of a base selected from triethylamine, pyridine, dimethyl aminopyridine and the like. The reaction may also be carried out in the presence of an acid such as H2SO4, HCl, HClO4, TFA, formic acid, Lewis acids like BF3, ZnCl2 etc. The reaction may be carried out in the presence of solvents such as dichloromethane, chloroform, C6H6, dimethyl sulfoxide, methanol, ethanol and the like or mixtures thereof. The reaction may be carried out at a temperature in the range of xe2x88x9270xc2x0 C. to 200xc2x0 C., preferably at a temperature in the range of xe2x88x9270xc2x0 C. to 160xc2x0 C. and the reaction time may range from 2 to 12 h, preferably from 2 to 10 h.
The protection of a compound of formula (VII) may be carried out using trityl chloride, t-butyldimethylsilyl chloride, pivaloyl chloride, dimethylsulfoxide, acetone, 2,2-dimethoxy propane, trimethyl ortho acetate, benzaldehyde, p-methoxy benzaldehyde, acetophenone and the like. The reaction may be carried out in the presence of a suitable catalyst such as SOCl2, H2SO4, HClO4, pyridinium p-toluene sulphonate, pyridine, p-toluene sulfonic acid, dimethyl aminopyridine, and the like. The reaction may be carried out in the absence or presence of suitable solvent such as benzene, DMF, dimethyl-sulfoxide (DMSO), acetonitrile, dichloromethane (DCM), and the like or mixtures thereof. The reaction may be carried out at a temperature in the range of 0xc2x0 C. to 60xc2x0 C., preferably at a temperature in the range of 20xc2x0 C. to 40xc2x0 C. The reaction time may range from 2 to 6 h, preferably from 2 to 4 h.
The reaction of a compound of formula (VIII) with a compound of formula (IX) may be carried out in the presence of dicyclohexylcarbodiimide (DCC), diethyl azadicarboxylate (DEAD), diisopropyl azadicarboxylate (DIAD), ethyl chloro formate and the like. The reaction may be carried out in the absence or presence of a base selected from triethylamine, pyridine, dimethyl aminopyridine and the like. The reaction may also be carried out in the presence of an acid such as H2SO4, HCl, HClO4, TFA, formic acid, and Lewis acids like BF3, ZnCl2 etc. The reaction may be carried out in the presence of solvents such as dichloromethane, chloroform, C6H6, dimethyl sulfoxide, methanol, ethanol and the like or mixtures thereof. The reaction may be carried out at a temperature in the range of xe2x88x9270xc2x0 C. to 200xc2x0 C., preferably at a temperature in the range of xe2x88x9270xc2x0 C. to 160xc2x0 C. and the reaction time may range from 2 to 12 h, preferably from 2 to 10 h.
The deprotection of a compound of formula (X) to produce a compound of formula (XI) may be carried out using deprotecting agent such as acetic acid, hydrochloric acid, formic acid, trifluoroacetic acid and the like. The reaction may be carried in the presence of suitable solvent such as water, THF, dioxane, DCM, CHCl3, methanol and the like or mixtures thereof. The reaction may be carried out at a temperature in the range of 0xc2x0 C. to 60xc2x0 C., preferably at a temperature in the range of 20xc2x0 C. to 40xc2x0 C. The reaction time may range from 2 to 6 h, preferably from 2 to 4 h.
The reaction of compound of formula (XI) with R2xe2x80x94L and/or R3xe2x80x94L, to produce a compound of formula (I) may be carried out in the presence of dicyclohexylcarbodiimide (DCC), diethyl azadicarboxylate (DEAD), diisopropyl azadicarboxylate (DIAD), ethyl chloroformate and the like. The reaction may be carried out in the absence or presence of a base selected from triethylamine, pyridine, dimethyl aminopyridine and the like. The reaction may also be carried out in the presence of an acid such as H2SO4, HCl, HClO4, TFA, formic acid, and Lewis acids like BF3, ZnCl2 etc. The reaction may be carried out in the presence of solvents such as dichloromethane, chloroform, C6H6, dimethyl sulfoxide, methanol, ethanol and the like or mixtures thereof. The reaction may be carried out at a temperature in the range of xe2x88x9270xc2x0 C. to 200xc2x0 C., preferably at a temperature in the range of xe2x88x9270xc2x0 C. to 160xc2x0 C. and the reaction time may range from 2 to 12 h, preferably from 2to 10 h.
The pharmaceutically acceptable salts are prepared by reacting the compounds of formula (I) with 1 to 4 equivalents of a base such as sodium hydroxide, sodium methoxide, sodium hydride, potassium t-butoxide, calcium hydroxide, magnesium hydroxide and the like, in solvents like ether, THF, methanol, t-butanol, dioxane, isopropanol, ethanol etc. A mixture of solvents may be used. Organic bases like lysine, arginine, diethanolamine, choline, guanidine and their derivatives etc. may also be used. Alternatively, acid addition salts wherever applicable are prepared by treatment with acids such as hydrochloric acid, phosphoric acid, p-toluenesulphonic acid, methanesulfonic acid, acetic acid, citric acid, maleic acid, salicylic acid, hydroxynaphthoic acid, ascorbic acid, palmitic acid, succinic acid, benzoic acid, benzenesulfonic acid, tartaric acid and the like in solvents like ethyl acetate, ether, alcohols, acetone, THF, dioxane etc. A mixture of solvents may also be used.
The stereoisomers of the compounds of formula (I) forming part of this invention may be prepared by using reactants in their single enantiomeric form in the process wherever possible or by conducting the reaction in the presence of reagents or catalysts in their single enantiomer form or by resolving the mixture of stereoisomers by conventional methods. Some of the preferred methods include use of microbial resolution, resolving the diastereomeric salts formed with chiral acids such as mandelic acid, camphorsulfonic acid, tartaric acid, lactic acid and the like or chiral bases such as brucine, cinchona alkaloids and their derivatives and the like. Commonly used methods are compiled by Jaques et al in xe2x80x9cEnantiomers, Racemates and Resolutionxe2x80x9d (Wiley Interscience, 1981).
Various polymorphs of the compounds of general formula (I) forming part of this invention may be prepared by crystallization of compound of formula (I) under different conditions. For example, using different solvents commonly used or their mixtures for recrystallization; crystallizations at different temperatures; various modes of cooling, ranging from very fast to very slow cooling during crystallizations. Polymorphs may also be obtained by heating or melting the compound followed by gradual or slow cooling. The presence of polymorphs may be determined by solid probe nmr spectroscopy, ir spectroscopy, differential scanning calorimetry, powder X-ray data or such other techniques.
Pharmaceutically acceptable solvates can be prepared by conventional methods such as dissolving the compounds of formula (I) in solvents such as water, methanol, ethanol etc., preferably water and recrystallizing by using different crystallization techniques.
The present invention also envisages pharmaceutical compositions containing compounds of the formula (I) defined earlier, their stereoisomers, their polymorphs, their pharmaceutically acceptable salts, their pharmaceutically acceptable solvates or their mixtures in combination with the usual pharmaceutically employed carriers, solvents, diluents and other media normally employed in preparing such compositions. The compositions may contain other active ingredients.
The pharmaceutical composition may be in the forms normally employed, such as tablets, capsules, powders, syrups, solutions, suspensions and the like, may contain flavourants, sweeteners etc. in suitable solid or liquid carriers or diluents, or in suitable sterile media to form injectable solutions or suspensions. Such compositions typically contain from 1 to 25%, preferably 1 to 15% by weight of active compound, the remainder of the composition may be pharmaceutically acceptable carriers, diluents or solvents and may also contain other active ingredients.
The compounds of the formula (I) as defined above are clinically administered to mammals, including man, via either oral or parenteral routes. Administration by the oral route is preferred, being more convenient and avoiding the possible pain and irritation of injection. However, in circumstances where the patient cannot swallow the medication, or absorption following oral administration is impaired, as by disease or other abnormality, it is essential that the drug be administered parenterally. By either route, the dosage is in the range of about 0.01 to about 100 mg/kg body weight of the subject per day or preferably about 0.01 to about 30 mg/kg body weight per day administered singly or as a divided dose. However, the optimum dosage for the individual subject being treated will be determined by the person responsible for treatment, generally smaller doses being administered initially and thereafter increments made to determine the most suitable dosage.
Suitable pharmaceutically acceptable carriers include solid fillers or diluents and sterile aqueous or organic solutions. The active compound will be present in such pharmaceutical compositions in the amounts sufficient to provide the desired dosage in the range as described above. Thus, for oral administration, the compounds can be combined with a suitable solid or liquid carrier or diluent to form capsules, tablets, powders, syrups, solutions, suspensions and the like. The pharmaceutical compositions, may, if desired, contain additional components such as flavourants, sweeteners, excipients and the like. For parenteral administration, the compounds can be combined with sterile aqueous or organic media to form injectable solutions or suspensions. For example, solutions in sesame or peanut oil, aqueous propylene glycol and the like can be used, as well as aqueous solutions of water-soluble pharmaceutically-acceptable acid addition salts or salts with base of the compounds. The injectable solutions prepared in this manner can then be administered intravenously, intraperitoneally, subcutaneously, or intramuscularly, with intramuscular administration being preferred in humans.
The invention is explained in detail in the examples given below which are provided by way of illustration only and therefore should not be construed to limit the scope of the invention.